Wireless power reception system, moving body, and wheel

ABSTRACT

A wireless power reception system  1  includes: a power reception device  5  including a power reception coil  51  that receives power supplied wirelessly from a power transmission coil  41  of a power transmission device  4  installed in a road surface, at least a portion of the power reception coil  51  being housed in a wheel  3  of a moving body  2 ; and an onboard device  6  which is installed in the moving body  2  and which is electrically connected to the power reception device  5 , wherein the power reception device  5  can transmit received power to the onboard device  6 , and the power reception coil  51  has a convex shape pointing downward in a side view as seen from an axial direction of the wheel  3.

TECHNICAL FIELD

The present disclosure relates to a wireless power reception system, amoving body, and a wheel.

BACKGROUND

In the related art, a wireless power transfer technology is known inwhich a power transmission device provided in a road surface, such as aroad or a parking lot, supplies power wirelessly to a power receptiondevice installed in a vehicle. For example, PTL 1 discloses a vehicleprovided with a power reception device on the underside of the vehicle,which enables the vehicle to receive power from a power transmissiondevice provided in a road surface.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Laid-Open No. 2018-068077

SUMMARY Technical Problem

However, in the wireless power transfer technology of the related artdescribed above, if the power transmission device provided in a roadsurface such as a road and the power reception device installed in avehicle that travels on the road are too far apart, an obstacle such asa small animal or piece of metal may come into the space between thepower transmission device and the power reception device, eddy currentsmay be generated around the obstacle, and the power reception efficiencymay be lowered. Moreover, the small animal, piece of metal, or the likethat has come between the power transmission device and the powerreception device may heat up and catch fire.

A purpose of the present disclosure devised in the light of suchcircumstances is to provide a wireless power reception system, a movingbody, and a wheel that can improve the power reception efficiency inwireless power transfer.

Solution to Problem

A wireless power reception system according to the present disclosureincludes:

a power reception device including a power reception coil that receivespower supplied wirelessly from a power transmission coil of a powertransmission device installed in a road surface, at least a portion ofthe power reception coil being housed in a wheel of a moving body; and

an onboard device which is installed in the moving body and which iselectrically connected to the power reception device, wherein

the power reception device can transmit the received power to theonboard device, and

the power reception coil has a convex shape pointing downward in a sideview as seen from an axial direction of the wheel.

A moving body according to the present disclosure includes:

a wheel;

a power reception device including a power reception coil that receivespower supplied wirelessly from a power transmission coil of a powertransmission device installed in a road surface, at least a portion ofthe power reception coil being housed in the wheel; and

an onboard device electrically connected to the power reception device,wherein

the power reception device can transmit the received power to theonboard device, and

the power reception coil has a convex shape pointing downward in a sideview as seen from an axial direction of the wheel.

A wheel according to the present disclosure is a wheel of a moving bodyand includes:

a power reception device including a power reception coil that receivespower supplied wirelessly from a power transmission coil of a powertransmission device installed in a road surface, wherein

at least a portion of the power reception coil is housed internally, and

the power reception coil has a convex shape pointing downward in a sideview as seen from an axial direction of the wheel.

Advantageous Effect

According to the present disclosure, it is possible to provide awireless power reception system, a moving body, and a wheel that canimprove the power reception efficiency in wireless power transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic diagram that uses a lateral cross section ofwheels to generally illustrate a wireless power reception systemaccording to an embodiment of the present disclosure;

FIG. 2 is a plan view illustrating an example of a power reception coil;

FIG. 3 is a cross section of the power reception coil taken along theline A-A in FIG. 2 ;

FIG. 4 is a cross section of the power reception coil taken along theline B-B in FIG. 3 ;

FIG. 5 is a cross section of the power reception coil taken along theline C-C in FIG. 3 ;

FIG. 6 is a perspective view schematically illustrating the windingstructure of a wire rod of the power reception coil in FIG. 2 ;

FIG. 7 is a schematic diagram that uses a lateral cross section of awheel to generally illustrate a tire and wheel assembly as one exampleof a wheel in a wireless power reception system according to anembodiment of the present disclosure;

FIG. 8 is a schematic diagram that generally illustrates a converter andan inverter of a power reception device housed in the wheel in FIG. 7 ;

FIG. 9 is a schematic diagram that generally illustrates an example of apower reception coil installed in a wheel; and

FIG. 10 is a schematic diagram that generally illustrates anotherexample of a power reception coil installed in a wheel.

DETAILED DESCRIPTION

Hereinafter, a wireless power reception system, moving body, and wheelaccording to an embodiment of the present disclosure will be describedwith reference to the drawings. In the drawings, common components andparts are denoted with the same signs. In this specification, thelateral direction of a wheel refers to the direction parallel to therotation axis of the wheel. The radial direction of a wheel refers tothe direction orthogonal to the rotation axis of the wheel.

(Configuration of Wireless Power Reception System)

FIG. 1 illustrates a schematic diagram that uses a lateral cross sectionof wheels to generally illustrate a wireless power reception system 1according to an embodiment of the present disclosure. The wireless powerreception system 1 is used so that a moving body 2 provided with a wheel3 receives power from a power transmission device 4 installed in a roadsurface. The wireless power reception system 1 includes a powerreception device 5 and an onboard device 6. The power reception device 5is housed, at least in part, in the wheel 3 of the moving body 2, andreceives power supplied wirelessly from a power transmission device 4installed in a road surface. The onboard device 6 is installed in themoving body 2 and is electrically connected to the power receptiondevice 5. When the moving body 2 travels or stops over the road surfacein which the power transmission device 4 is installed, the powerreception device 5 receives power wirelessly from the power transmissiondevice 4. The power reception device 5 transmits the received power tothe onboard device 6.

The wireless power reception system 1 may further include a controldevice 7. The control device 7 is communicably connected to the powerreception device 5 and the onboard device 6 through an in-vehiclenetwork such as a controller area network (CAN). The control device 7can control the power reception device 5 and the onboard device 6 suchthat power received wirelessly by the power reception device 5 istransmitted to the onboard device 6. The positions and numbers of thewheel 3, power reception device 5, onboard device 6, and control device7 in the moving body 2 illustrated in FIG. 1 are an example and may bedetermined freely to suit the purpose and the like of each device.

The moving body 2 can travel over a road surface such as a road via thewheel 3. The moving body 2 is an automobile for example, but is notlimited thereto. The moving body 2 may be any vehicle capable oftraveling over a road surface via the wheel 3, including an automobilesuch as a passenger vehicle, a truck, a bus, or a motorcycle, anagricultural vehicle such as a tractor, an industrial or constructionvehicle such as a dump truck, an aircraft, a bicycle, or a wheelchair.

The wheel 3 is used to move the moving body 2. The wheel 3 has a contactpatch that contacts the road surface such as a road while attached tothe moving body 2. In the present embodiment, each wheel 3 is a tire andwheel assembly obtained by mounting a tire 31 onto a wheel 32, but thewheel 3 is not limited thereto and may be any wheel that can be attachedto the moving body 2 described above. In the case where the wheel 3 is atire and wheel assembly, the “contact patch” of the wheel 3 refers tothe contact patch of the tire 31, or in other words, the surface of thetire 31 that touches the road surface in the state in which the tire 31is mounted onto an applicable rim, inflated to a prescribed internalpressure, and subjected to a maximum load.

In this specification, an “applicable rim” refers to a valid industrialstandard in the region where a pneumatic tire is manufactured and used,namely, an approved rim for an applicable size described in apublication such as the JATMA Year Book of the Japan Automobile TyreManufacturers Association (JATMA) in Japan, the Standards Manual of theEuropean Tyre and Rim Technical Organization (ETRTO) in Europe, or theYear Book of the Tire and Rim Association, Inc. (TRA) in the UnitedStates or to be described in the future (the Measuring Rim in the ETRTOStandards Manual or the Design Rim in the TRA Year Book), but in thecase of a size not described in the above industrial standards, theapplicable rim refers to a rim of a width corresponding to the beadwidth of the pneumatic tire. The “applicable rim” includes current sizesin addition to sizes that may be included in the above industrialstandards in the future. The “sizes to be described in the future” mayinclude the sizes described as “Future Developments” in the ETRTO 2013edition, for example.

In this specification, the “prescribed internal pressure” refers to theair pressure (maximum air pressure) corresponding to the maximum loadcapability of a single wheel for the applicable size and ply ratingdescribed in an industrial standard such as the JATMA Year Bookdescribed above, but in the case of a size not described in the aboveindustrial standards, the prescribed internal pressure refers to the airpressure (maximum air pressure) corresponding to the maximum loadcapability prescribed for each vehicle on which the tires are mounted.Also, in this specification, the “maximum load” refers to the loadcorresponding to the maximum load capability for a tire of applicablesize described in the above industrial standards, or in the case of asize not described in the above industrial standards, the loadcorresponding to the maximum load capability prescribed for each vehicleon which the tires are mounted.

FIG. 1 illustrates a schematic diagram that uses a lateral cross sectionof the wheels 3 to generally illustrate a tire and wheel assembly as oneexample of the wheel 3 in the wireless power reception system 1according to an embodiment of the present disclosure.

As illustrated in FIG. 1 , each tire 31 includes a pair of bead portions311, a pair of sidewall portions 312, and a tread portion 313. The beadportions 311 are configured such that the inner radial side and outerlateral side touch a rim portion 321 of the wheel 32 when the tire 31 ismounted onto the rim portion 321. The sidewall portions 312 extendbetween the tread portion 313 and the bead portions 311. The sidewallportions 312 are positioned farther radially outward than the beadportions 311. The tread portion 313 is positioned farther radiallyoutward than the sidewall portions 312, and may include the contactpatch of the tire 31.

The tire 31 is formed using a rubber such as natural rubber or syntheticrubber, and may include parts such as a carcass, a belt, and bead wiresformed using a metal such as steel. For example, at least a portion ofthe parts such as the carcass, belt, and bead wires may also be formedusing a nonmagnetic material. With this configuration, the strength ofthe tire 31 can be maintained, while in addition, due to the existenceof a metal between the power transmission device 4 and the powerreception device 5, the tire 31 can lessen the attenuation of a magneticfield generated by the power transmission device 4 before the magneticfield reaches the power reception device 5, and by extension, improvethe power reception efficiency of the power reception device 5 whenwireless power transfer from the power transmission device 4 to thepower reception device 5 is performed by electromagnetic induction, asdescribed later. However, at least a portion of the parts such as thecarcass, belt, and bead wires does not have to be formed using anonmagnetic material.

The nonmagnetic material may include a paramagnetic material or adiamagnetic material having a low permeability. For example, a resinmaterial containing a thermoplastic resin such as polyester or nylon, athermosetting resin such as a vinyl ester resin or an unsaturatedpolyester resin, or some other synthetic resin can be used as thenonmagnetic material. Furthermore, fibers of a material such as glass,carbon, graphite, aramid, polyethylene, or ceramic can be included inthe resin material as reinforcing fibers. The nonmagnetic material isnot limited to a resin, and any nonmetallic material containing rubber,glass, carbon, graphite, aramid, polyethylene, ceramic, or the like canbe used. Furthermore, a metal material containing a paramagneticmaterial such as aluminum or a diamagnetic material such as copper canbe used as the nonmagnetic material.

The wheel 32 includes a cylindrical rim portion 321 for mounting thetire 31 and a disc portion 322 which is provided on the inner radialside of the rim portion 321 and which is supported by and secured to ahub 21 of the moving body 2.

The wheel 32 may be formed using a metal such as steel, but is notlimited thereto. At least a portion of the rim portion 321 of the wheel32 may also be formed using the nonmagnetic material described above.With this configuration, the strength of the wheel 32 can be maintained,while in addition, due to the existence of a metal such as steel betweenthe power transmission device 4 and the power reception device 5, thewheel 32 can lessen the attenuation of a magnetic field generated by thepower transmission device 4 before the magnetic field reaches the powerreception device 5, and by extension, improve the power receptionefficiency of the power reception device 5. However, at least a portionof the rim portion 321 of the wheel 32 does not have to be formed usinga nonmagnetic material.

Referring to FIG. 1 , the power transmission device 4 is provided with apower transmission coil (primary coil) 41. The power transmission device4 is installed in a road surface such as a road or a parking lot. In thepresent embodiment, the power transmission device 4 is embedded in aroad or the like, but may also be installed such that at least a portionis exposed on the road surface. In the diagram, the power transmissioncoil 41 is illustrated schematically for simplicity.

The power transmission coil 41 generates an AC magnetic field on thebasis of an AC current supplied from a power source. In the presentembodiment, the power transmission coil 41 is configured into a loopoverall. In this specification, the plane enclosed by the looped powertransmission coil 41 is also referred to as the coil plane of the powertransmission coil 41. To generate an AC magnetic field directed abovethe road surface, the power transmission coil 41 is disposed such thatthe coil plane of the power transmission coil 41 is approximatelyparallel to the road surface (in other words, the axial direction of thepower transmission coil 41 is approximately perpendicular to the roadsurface). The power transmission coil 41 provided in the powertransmission device 4 is wound around a core such as a ferrite core andconfigured into a loop overall, for example, but is not limited thereto,and may be any type of coil that can generate an AC magnetic field, suchas a coil spring or an air core coil. With this configuration, when thewheel 3 passes over the power transmission device 4 while the movingbody 2 is traveling or the like, wireless power transfer from the powertransmission coil 41 to a power reception coil 51 may be performed byelectromagnetic induction.

The power reception device 5 is provided with a power reception coil(secondary coil) 51. The power reception coil 51 receives power suppliedwirelessly from the power transmission coil 41 of the power transmissiondevice 4. In the present embodiment, the power reception coil 51 isconfigured into a loop overall. In this specification, the planeenclosed by the looped power reception coil 51 is also referred to asthe coil plane of the power reception coil 51. The power reception coil51 is disposed such that the coil plane of the power reception coil 51is approximately parallel to the contact patch of the wheel 3 (in otherwords, the axial direction of the power reception coil 51 isapproximately perpendicular to the road surface). With this arrangement,an electromotive force is generated by electromagnetic induction and acurrent flows in the power reception coil 51 on the basis of the ACmagnetic field generated by the power transmission coil 41. In thediagram, the power reception coil 51 is illustrated schematically forsimplicity.

At least a portion of the power reception coil 51 is housed in the wheel3 of the moving body 2. In the present embodiment, at least a portion(preferably all) of the coil plane of the power reception coil 51 facesthe contact patch of the wheel 3. With this arrangement, in the casewhere the contact patch of the wheel 3 is positioned above the powertransmission coil 41, including the case where the coil plane of thepower reception coil 51 does not extend approximately parallel to thecontact patch of the wheel 3, at least a portion of the coil plane ofthe power reception coil 51 can face at least a portion of the coilplane of the power transmission coil 41 with the contact patch of thewheel 3 in between. Consequently, the possibility of an obstacle comingbetween the power transmission coil 41 and the power reception coil 51may be lowered, and additionally, the magnetic field lines emitted fromthe power transmission coil 41 can be received appropriately by thepower reception coil 51. Consequently, the power reception efficiency inwireless power transfer may be improved further.

Here, in this specification, (at least a portion of) a plane A “facing”a plane B for example refers to (at least a portion of) the plane Aoverlapping inside a region extending perpendicular to the plane B inthe range over which the plane B extends (in other words, inside thepillar-shaped region having the plane B as its cross section).

In this specification, at least a portion (preferably all) of thecontact patch of the wheel 3 faces the coil plane of the power receptioncoil 51. From the standpoint of further raising the power receptionefficiency, it is preferable if at least a portion (preferably all) ofthe coil plane of the power reception coil 51 faces the contact patch ofthe wheel 3, and/or at least a portion (preferably all) of the contactpatch of the wheel 3 faces the coil plane of the power reception coil51, like in the present embodiment.

The power reception coil 51 of the power reception device 5 is housed inthe wheel 3 of the moving body 2 so as not to rotate together with thewheel 3. For example, as illustrated in FIG. 1 , the power receptioncoil 51 may be installed in a portion that is attached to the wheel 3from the inner radial side of the wheel 3, such as a cover 21 a of thehub 21 in the moving body 2. With this arrangement, at least a portionof the power reception coil 51 is housed on the inner radial side of thewheel 32 in the state where the wheel 32 of the wheel 3 is attached tothe hub 21 of the moving body 2.

In addition to the power reception coil 51, the power reception device 5additionally may be provided with a power converter, a power storageunit, a measurement unit, and the like.

The power converter is provided with a converter that converts AC powerto DC power, an inverter that converts DC power to AC power, and thelike.

The power storage unit stores power generated in the power receptioncoil 51. The power storage unit may be a capacitor, for example. In thecase where the power storage unit is a capacitor, charging anddischarging can be performed in a short time compared to a storagebattery or the like, which is advantageous in situations demanding highresponsiveness.

The measurement unit measures the strength of the power received by thepower reception device 5. The measurement unit is a voltmeter or anammeter for example, but is not limited thereto. The strength of thepower measured by the measurement unit may include numerical informationof any type, such as electric power, electric energy, voltage, current,magnetic flux, or magnetic flux density for example.

Hereinafter, FIGS. 2 to 6 will be referenced to describe an example ofthe power reception device 5 more specifically. The power receptiondevice 5 is provided with the power reception coil 51 and a coil case55. FIG. 2 is a plan view illustrating the power reception coil 51 asviewed from the direction orthogonal to the coil plane. FIG. 3 is across section of the power reception coil 51 and the coil case 55 takenalong the line A-A in FIG. 2 . FIG. 4 is a cross section of the powerreception coil 51 and the coil case 55 taken along the line B-B in FIG.3 , and FIG. 5 is a cross section of the power reception coil 51 and thecoil case 55 taken along the line C-C in FIG. 3 . FIG. 6 is aperspective view schematically illustrating the winding structure of awire rod 53 forming the power reception coil 51. Note that in FIGS. 4and 5 , the wire rod 53 is omitted from illustration to make it easy tounderstand the shapes of spiral grooves 55 g and 55 h. In FIG. 6 , afirst spiral coil layer 52 a is indicated by dashed lines and a secondspiral coil layer 52 b is indicated by solid lines.

The power reception coil 51 can be configured in a multilayer structureincluding a stacked plurality of spiral coil layers 52 a and 52 b. Thepower reception coil 51 illustrated in FIGS. 2 to 6 has a two-layerstructure including a first spiral coil layer 52 a and a second spiralcoil layer 52 b stacked on top of one another. The power reception coil51 is disposed such that the first spiral coil layer 52 a faces thepower transmission coil 41. In the power reception coil 51 installed inthe moving body 2, the first spiral coil layer 52 a is positioned lowerthan the second spiral coil layer 52 b in the vertical direction. Notethat the power reception coil 51 may also have three or more stackedspiral coil layers.

As illustrated in FIG. 2 , the first spiral coil layer 52 a and thesecond spiral coil layer 52 b are placed on top of each other such thattheir central axes are positioned on the same straight line.

The spiral coil layers 52 a and 52 b are formed by winding the wire rod53 into a spiral shape on the same surface (in this example, in the sameplane). The extension direction of the central axes of the spiral coillayers 52 a and 52 b obtained by the winding of the wire rod 53 istreated as the axial direction of the power reception coil 51.

The wire rod 53 forming each of the spiral coil layers 52 a and 52 b iscontinuous throughout. The wire rod 53 forming the first spiral coillayer 52 a and the wire rod 53 forming the second spiral coil layer 52 bare continuous in an inner circumferential peripheral portion of each ofthe spiral coil layers 52 a and 52 b. In other words, a connectingportion 54 between the first spiral coil layer 52 a and the secondspiral coil layer 52 b is positioned in an inner circumferentialperipheral portion of the power reception coil 51 (an innercircumferential peripheral portion of each of the spiral coil layers 52a and 52 b). Note that the wire rod 53 forming the first spiral coillayer 52 a and the wire rod 53 forming the second spiral coil layer 52 bdo not have to be continuous in an inner circumferential peripheralportion of each of the spiral coil layers 52 a and 52 b. Moreover, theposition of the connecting portion 54 is not limited to the innercircumferential peripheral portion of the power reception coil 51, andmay also be provided in an outer circumferential peripheral portion ofthe power reception coil 51, for example. The wire rod 53 forming thefirst spiral coil layer 52 a and the wire rod 53 forming the secondspiral coil layer 52 b may be joined by welding, pressure welding, orthe like in the connecting portion 54, or as described later, the firstspiral coil layer 52 a and the second spiral coil layer 52 b, includingthe connecting portion 54, may be formed by winding a single continuouswire rod 53.

The connecting portion 54 is preferably inclined with respect to theaxial direction of the power reception coil 51, but may also be parallelto the axial direction of the power reception coil 51 (perpendicular tothe coil plane of the power reception coil 51). In this example, theconnecting portion 54 is inclined gently in the thickness direction ofthe power reception coil 51. Specifically, the connecting portion 54 isinclined so as to intersect with both the wire rod 53 forming the firstspiral coil layer 52 a and the wire rod 53 forming the second spiralcoil layer 52 b at obtuse angles (angles greater than 90° and less than180°).

The first spiral coil layer 52 a and the second spiral coil layer 52 bare formed by winding a single continuous wire rod 53. That is, thefirst spiral coil layer 52 a and the second spiral coil layer 52 b,including the connecting portion 54, are formed by a single continuouswire rod 53. Note that a “single continuous wire rod 53” means a wirerod formed integrally as a whole, and includes litz wire containingmultiple twisted strands of enameled wires, for example. Moreover, thewire rod 53 is preferably litz wire, but is not limited thereto and mayalso be solid wire, for example.

As illustrated in FIG. 6 , the wire rod 53 forming the power receptioncoil 51 extends in a spiral from a winding start end (an end 53 a of thewire rod 53) positioned on the outer circumferential peripheral side ofthe first spiral coil layer 52 a and proceeding radially inward to forman approximately rectangular (more specifically, an approximatelysquare) coil plane overall, joins the connecting portion 54 inclinedwith respect to the coil plane in the inner circumferential peripheralportion, and the connecting portion 54 smoothly joins the innercircumferential peripheral portion of the second spiral coil layer 52 b.In addition, the wire rod 53 extends in a spiral shape from the innercircumferential peripheral portion of the second spiral coil layer 52 bproceeding radially outward similarly to the first spiral coil layer 52a, and a winding terminal end (another end 53 b of the wire rod 53) ispositioned on the outer circumferential peripheral side. The end 53 aand the other end 53 b of the wire rod 53 are disposed on the same sidesurface 55 f of the rectangular plate-shaped coil case 55 describedlater. Also, the end 53 a and the other end 53 b of the wire rod 53 arerespectively positioned near either end of the side surface 55 f in thelongitudinal direction. By adopting such a configuration, the end 53 aand the other end 53 b can be disposed at positions that are fartherapart.

The power reception device 5 is provided with the coil case 55 thatsupports the wire rod 53. The coil case 55 includes a case body 55 a(wire rod support portion) formed using a resin containing an insulatingmaterial, a first cover 55 b that covers the front surface of the casebody 55 a, and a second cover 55 c that covers the back surface of thecase body 55 a. The first cover 55 b and the second cover 55 c areformed using a resin containing an insulating material. The coil case 55in this example includes a third cover 55 d provided on the outside(back side) of the second cover 55 c. The third cover 55 d may be formedusing a resin or a metal such as aluminum.

The first spiral coil layer 52 a is held between the case body 55 a andthe first cover 55 b, while the second spiral coil layer 52 b is heldbetween the case body 55 a and the second cover 55 c. With thisarrangement, the wire rod 53 forming the power reception coil 51 ishoused inside the coil case 55, except for the ends 53 a and 53 b oneither side. Consequently, it is possible to keep dust and the like fromadhering to the wire rod 53.

The case body 55 a, first cover 55 b, second cover 55 c, and third cover55 d forming the coil case 55 are fastened to one another by fasteningmembers such as screws, or secured to one another by gluing, welding, orthe like.

The coil case 55 has a space 55 e between the second cover 55 c and thethird cover 55 d, into which a plate-shaped magnetic body (ferritemember) or the like can be placed. By placing a magnetic body in thespace 55 e, or in other words, by providing a magnetic body on the backside of the second spiral coil layer 52 b, the power receptionefficiency of the power reception coil 51 can be raised.

Note that a magnetic body such as a ferrite core may also be providedfarther inward (toward the central axis) than the inner circumferentialperipheral portion of the power reception coil 51. In this case, a spacefor placing a magnetic body can be provided in the central portion ofthe case body 55 a, for example.

The coil case 55 is formed into a flat plate shape overall. In addition,the coil case 55 has a rectangular shape, more specifically anapproximately square shape, in a planar view from the axial direction ofthe power reception coil 51. However, the coil case 55 may also have adifferent shape in the same planar view. Also, the case body 55 a, firstcover 55 b, second cover 55 c, and third cover 55 d forming the coilcase 55 similarly have a rectangular plate shape in a planar view, andare disposed overlapping in the thickness direction of the coil case 55.Note that the coil case 55 is not limited to a flat case like in thisexample and may also be curved, bent, or have depressed or raisedportions.

The spiral grooves 55 g and 55 h are formed on the front surface and theback surface, respectively, of the case body 55 a, and the wire rod 53is disposed to follow the spiral grooves 55 g and 55 h. The wire rod 53disposed to follow the spiral groove 55 g on the front surface of thecase body 55 a forms the first spiral coil layer 52 a, and the wire rod53 disposed to follow the spiral groove 55 h on the back surface of thecase body 55 a forms the second spiral coil layer 52 b. A partition wall55 j is provided between the spiral groove 55 g on the front surface andthe spiral groove 55 h on the back surface of the case body 55 a.

The spiral groove 55 g on the front surface and the spiral groove 55 hon the back surface of the case body 55 a are spaced apart by apredetermined distance (at least the thickness of the partition wall 55j or more) in the thickness direction (axial direction of the powerreception coil 51) of the case body 55 a by the partition wall 55 j.Additionally, the spiral groove 55 g on the front surface and the spiralgroove 55 h on the back surface communicate through a through-hole 55 kformed in the partition wall 55 j. The through-hole 55 k penetrates fromthe groove bottom of the spiral groove 55 g on the front surface (frontsurface of the partition wall 55 j) to the groove bottom of the spiralgroove 55 h on the back surface (back surface of the partition wall 55j).

The through-hole 55 k is formed at a position corresponding to theconnecting portion 54 of the power reception coil 51. Consequently, theposition of the through-hole 55 k can be adjusted, as appropriate, incorrespondence with the position of the connecting portion 54 of thepower reception coil 51. In this example, the through-hole 55 k ispositioned in the central part of the case body 55 a, and morespecifically, at a position corresponding to the inner circumferentialperipheral portion of the power reception coil 51. With thisarrangement, the connecting portion 54 of the power reception coil 51can be disposed in the through-hole 55 k.

Referring to FIG. 1 again, the onboard device 6 is installed in themoving body 2 and is electrically connected to the power receptiondevice 5. The power reception device 5 and the onboard device 6 may beelectrically connected in a wired way. In such a case, the powertransmission efficiency from the power reception device 5 to the onboarddevice 6 is improved compared to the case of a wireless connection.Also, the power reception device 5 and the onboard device 6 may beelectrically connected in a wireless way. In such a case, for example,it is unnecessary to run power lines for transmitting power from thepower reception device 5 to the onboard device 6 installed in the bodyof the moving body 2 away from the wheel 3, thereby lowering thepossibility that the power lines may be severed in association with therotation of the wheel 3.

The onboard device 6 may also include a driving device 61 that drivesthe wheel 3 with electric power, for example. In such a case, thedriving device 61 consumes power supplied from the power receptiondevice 5 to drive the wheel 3. In the present embodiment, the drivingdevice 61 is an in-wheel motor housed, at least in part, in the wheel 3,but is not limited thereto. The driving device 61 may also be an onboardmotor which is installed in the body of the moving body 2 and whichcauses the wheel 3 to be driven by driving a shaft 22 of the moving body2.

As another example, the onboard device 6 may also include a powerstorage device 62 that stores electric power. The power storage device62 can store electric power supplied from the power reception device 5and also supply electric power to other onboard devices 6. For example,the power storage device 62 may be a storage battery of any type, suchas a lead storage battery, a nickel hydride battery, a lithium-ionbattery, a sodium-sulfur battery, or a combination of the above.

The onboard device 6 is not limited to the examples described above andmay also include any electronic devices installed in the moving body 2,such as a communication device for the moving body 2, a car navigationsystem, a media player, and in-vehicle sensors. The onboard device 6 maybe integrated into the moving body 2 or removably installed in themoving body 2.

Hereinafter, FIGS. 7 and 8 will be referenced to describe an example ofthe power reception device 5 and the driving device 61 specifically.FIG. 7 is a schematic diagram that uses a lateral cross section of thewheel 3 to generally illustrate a tire and wheel assembly as one exampleof the wheel 3 in the wireless power reception system 1. FIG. 8 is aschematic diagram that generally illustrates a converter 56 a and aninverter 56 b of the power reception device 5 housed in the wheel 3 inFIG. 7 . In this example, the driving device 61 is an in-wheel motorinstalled in the wheel 3, and is housed, at least in part, in the wheel3.

As illustrated in FIGS. 7 and 8 , the power reception device 5 isprovided with the converter 56 a and the inverter 56 b as powerconverters. The converter 56 a is connected to the power reception coil51 and the inverter 56 b. The converter 56 a can convert AC powergenerated in the power reception coil 51 into DC power, and transmitpower to the inverter 56 b. The inverter 56 b is connected to theconverter 56 a and the driving device 61. The inverter 56 b can convertDC power from the converter 56 a into AC power, and transmit power tothe driving device 61.

The converter 56 a is positioned vertically above the power receptioncoil 51, and the inverter 56 b is positioned vertically above theconverter 56 a. In this example, the entire converter 56 a and theentire inverter 56 b are housed in the wheel 3. Note that it issufficient if at least a portion of the converter 56 a and the inverter56 b are housed in the wheel 3.

The converter 56 a and the inverter 56 b are provided on an annularsubstrate 56 c disposed coaxially with the wheel 3. The power receptioncoil 51 is positioned below the substrate 56 c. Note that the powerreception coil 51 may also at a position that overlaps with thesubstrate 56 c in the vertical direction.

As illustrated in FIG. 8 , the converter 56 a and the inverter 56 b aredisposed at different circumferential positions on the annular substrate56 c. The converter 56 a and the inverter 56 b are disposedconcentrically on the substrate 56 c. The converter 56 a is positionedin a lower portion of the substrate 56 c, and the inverter 56 b ispositioned in an upper portion of the substrate 56 c.

The driving device 61 is a direct drive motor 63 disposed coaxially withthe wheel 3. The direct drive motor 63 is disposed coaxially with thewheel 3. In addition, the direct drive motor 63 is housed entirely inthe wheel 3. Note that it is sufficient if at least a portion of thedirect drive motor 63 is housed in the wheel 3.

The power reception device 5 includes the coil case 55 housing the powerreception coil 51. The coil case 55 is provided integrally with a case56 d that houses the converter 56 a. Note that the coil case 55 may alsobe joined to the case 56 d. Also, the coil case 55 may be providedindependently from the case 56 d that houses the converter 56 a. Thecase 56 d is housed entirely in the wheel 3. The case 56 d encloses thesubstrate 56 c, the converter 56 a, the inverter 56 b, and the directdrive motor 63 from the outside. Note that the case 56 d that houses theconverter 56 a is not a required component.

The control device 7 controls at least one of the power reception device5 or the onboard device 6. The control device 7 is an electronic controlunit (ECU), for example, but is not limited thereto and may beelectronic equipment of any type. The control device 7 may also beelectrically connected to the power reception device 5 as one of theonboard devices 6 described above.

The control device 7 may be provided with a control unit, a storageunit, a communication unit, an output unit, an input unit, and the like,for example. For example, the control device 7 can cause the powerreception device 5 to transmit power received wirelessly by the powerreception device 5 to at least one of a plurality of onboard devices 6,including the driving device 61 and the power storage device 62 forexample, on the basis of a predetermined condition.

Hereinafter, FIGS. 9 and 10 will be referenced to describe anotherexample of the power reception coil 51 specifically. The power receptioncoil 51 illustrated in FIG. 9 has a convex shape pointing downward in aside view as seen from the axial direction of the wheel 3. FIG. 9schematically illustrates only the wheel 3 and the power reception coil51. Also, in FIG. 9 , a power reception coil 51 a having a flat shapeextending horizontally in a side view as seen from the axial directionof the wheel 3 is indicated by a chain double-dashed line forcomparison. Also, in FIG. 9 , a power reception coil 51 b having aconvex bent shape pointing downward in a side view is indicated by achain double-dashed line for comparison. The power reception coil 51 bhas the same width and the same height as the power reception coil 51 ina side view. Note that the power reception coil 51 illustrated in FIG. 9has a single-layer structure including a single spiral coil layer, butis not limited thereto.

The power reception coil 51 illustrated in FIG. 9 is curved into an arcshape overall in a side view. The power reception coil 51 is not limitedto a shape curved into an arc and may be configured to have at least aconvex, non-flat shape pointing downward overall, such as by being bentinto a downward-pointing V-shape like the power reception coil 51 b, forexample. Also, although omitted from illustration in the diagram, thepower reception device 5 may also include a curved coil casecorresponding to the shape of the power reception coil 51.

In the power reception coil 51 illustrated in FIG. 9 , the center ofcurvature P of the power reception coil 51 in a side view is located onthe central axis of the wheel 3. With this arrangement, the powerreception coil 51 can be disposed to follow the inner circumferentialsurface 3 a of the wheel 3. Note that the inner circumferential surface3 a of the wheel 3 can be taken to be the inner circumferential surfaceof the rim portion 321, for example, but is not limited thereto.

The power reception coil 51 illustrated in FIG. 10 includes a stackedplurality of spiral coil layers 52 c and 52 d. FIG. 10 schematicallyillustrates only the wheel 3 and the power reception coil 51. Also, inFIG. 10 , a power reception coil 51 c having a single-layer structureincluding a single spiral coil layer is indicated by a chaindouble-dashed line for comparison. In the case where the power receptioncoil is long in the wheel circumferential direction like the powerreception coil 51 c, the ends of the power reception coil 51 c in thewheel circumferential direction become distant from the powertransmission coil 41 more easily. For this reason, by configuring thepower reception coil 51 to have a multilayer structure including theplurality of spiral coil layers 52 c and 52 d to reduce the length inthe wheel circumferential direction, the average distance between thepower transmission coil 41 installed in a road surface and the powerreception coil 51 can be reduced, as illustrated in FIG. 10 . Note thatin the power reception coil 51 illustrated in FIG. 10 , the center ofcurvature P of the power reception coil 51 in a side view likewise islocated on the central axis of the wheel 3, but is not limited thereto.Also, the power reception coil 51 in FIG. 10 has two layers includingthe spiral coil layers 52 c and 52 d, but may also have three or morespiral coil layers.

Other than being curved in a side view, the power reception coil 51illustrated in FIG. 10 can be configured similarly to the powerreception coil 51 having the multilayer structure described withreference to FIGS. 2 to 6 . For example, the two spiral coil layers 52 cand 52 d may be wound using a single, continuous wire rod 53.Additionally, the power reception device 5 may be provided with a curvedcoil case 55 in correspondence with the power reception coil 51. In thiscase, the coil case 55 may be provided with the case body 55 a (wire rodsupport portion), the first cover 55 b, the second cover 55 c, the thirdcover 55 d, and the like having curved shapes corresponding to the shapeof the power reception coil 51. Moreover, the two spiral coil layers 52c and 52 d may also be formed by disposing the wire rod 53 to followspiral grooves provided on the front and back surfaces of the case body55 a.

As described above, the wireless power reception system 1 according toan embodiment of the present disclosure includes: the power receptiondevice 5 including the power reception coil 51 that receives powersupplied wirelessly from the power transmission coil 41 of the powertransmission device 4 installed in a road surface, at least a portion ofthe power reception coil 51 being housed in the wheel 3 of the movingbody 2; and the onboard device 6 which is installed in the moving body 2and which is electrically connected to the power reception device 5,wherein the power reception device 5 can transmit received power to theonboard device 6, and the power reception coil 51 has a convex shapepointing downward in a side view as seen from the axial direction of thewheel 3. According to such a configuration, by housing at least aportion of the power reception coil 51 in the wheel 3 that directlycontacts the road surface, it is possible to lower the possibility thatan obstacle will come into the space between the power transmission coil41 provided in the road surface and the power reception coil 51. Forthis reason, the wireless power reception system 1 can improve the powerreception efficiency in wireless power transfer.

Also, according to the wireless power reception system 1 according to anembodiment of the present disclosure, since the power reception coil 51has a convex shape pointed downward in a side view as seen from theaxial direction of the wheel 3, the average distance between the powertransmission coil 41 installed in a road surface and the power receptioncoil 51 can be reduced compared to the power reception coil 51 a havinga flat shape extending horizontally in a side view. As a result, thepower transfer efficiency of the wireless power reception system 1including the power reception coil 51 can be raised.

In the wireless power reception system 1 according to an embodiment ofthe present disclosure, the power reception coil 51 is curved into anarc shape in a side view. According to such a configuration, the averagedistance between the power transmission coil 41 and the power receptioncoil 51 can be reduced further, and the power transfer efficiency of thewireless power reception system 1 can be raised further compared to thepower reception coil 51 b bent into a V-shape with the same width andthe same height in a side view, for example.

In the wireless power reception system 1 according to an embodiment ofthe present disclosure, the center of curvature P of the power receptioncoil 51 in a side view is located on the central axis of the wheel 3.According to such a configuration, since the power reception coil 51 canbe disposed to follow the inner circumferential surface 3 a of the wheel3, the average distance between the power transmission coil 41 and thepower reception coil 51 can be reduced further, and the power transferefficiency of the wireless power reception system 1 can be raisedfurther. In addition, by disposing the power reception coil 51 to followthe inner circumferential surface 3 a of the wheel 3, the space insidethe wheel 3 can be utilized effectively.

In the wireless power reception system 1 according to an embodiment ofthe present disclosure, the power reception coil 51 includes a stackedplurality of spiral coil layers 52 c and 52 d. According to such aconfiguration, the length of the power reception coil 51 in thecircumferential direction of the wheel 3 in a side view can be reducedcompared to the power reception coil 51 c having a single-layerstructure including a single spiral coil layer. For this reason, theaverage distance between the power transmission coil 41 installed in aroad surface and the power reception coil 51 can be reduced further, andthe power transfer efficiency can be raised further.

The moving body 2 according to an embodiment of the present disclosureincludes: the wheel 3; the power reception device 5 including the powerreception coil 51 that receives power supplied wirelessly from the powertransmission coil 41 of the power transmission device 4 installed in aroad surface, at least a portion of the power reception coil 51 beinghoused in the wheel 3; and the onboard device 6 electrically connectedto the power reception device 5, wherein the power reception device 5can transmit received power to the onboard device 6, and the powerreception coil 51 has a convex shape pointing downward in a side view asseen from the axial direction of the wheel 3. According to such aconfiguration, by housing at least a portion of the power reception coil51 in the wheel 3 that directly contacts the road surface, it ispossible to lower the possibility that an obstacle will come into thespace between the power transmission coil 41 provided in the roadsurface and the power reception coil 51. For this reason, the movingbody 2 can improve the power reception efficiency in wireless powertransfer. Also, since the power reception coil 51 has a convex shapepointed downward in a side view as seen from the axial direction of thewheel 3, the average distance between the power transmission coil 41installed in a road surface and the power reception coil 51 can bereduced compared to the power reception coil 51 a having a flat shapeextending horizontally in a side view. As a result, the power transferefficiency of the wireless power reception system 1 including the powerreception coil 51 can be raised.

The wheel 3 according to an embodiment of the present disclosure is awheel 3 of the moving body 2 and includes: the power reception device 5including the power reception coil 51 that receives power suppliedwirelessly from the power transmission coil 41 of the power transmissiondevice 4 installed in a road surface, wherein at least a portion of thepower reception coil 51 is housed in the wheel 3, and the powerreception coil 51 has a convex shape pointing downward in a side view asseen from the axial direction of the wheel 3. According to such aconfiguration, by housing at least a portion of the power reception coil51 in the wheel 3 that directly contacts the road surface, it ispossible to lower the possibility that an obstacle will come into thespace between the power transmission coil 41 provided in the roadsurface and the power reception coil 51. For this reason, the wheel 3can improve the power reception efficiency in wireless power transfer.Also, since the power reception coil 51 has a convex shape pointeddownward in a side view as seen from the axial direction of the wheel 3,the average distance between the power transmission coil 41 installed ina road surface and the power reception coil 51 can be reduced comparedto the power reception coil 51 a having a flat shape extendinghorizontally in a side view. As a result, the power transfer efficiencyof the wireless power reception system 1 including the power receptioncoil 51 can be raised.

Also, the wireless power reception system 1 embodied as illustrated inFIGS. 2 to 6 includes: the power reception device 5 including the powerreception coil 51 that receives power supplied wirelessly from the powertransmission coil 41 of the power transmission device 4 installed in aroad surface, at least a portion of the power reception coil 51 beinghoused in the wheel 3 of the moving body 2; and the onboard device 6which is installed in the moving body 2 and which is electricallyconnected to the power reception device 5, wherein the power receptiondevice 5 transmits received power to the onboard device 6. According tosuch a configuration, by housing at least a portion of the powerreception coil 51 in the wheel 3 that directly contacts the roadsurface, it is possible to lower the possibility that an obstacle willcome into the space between the power transmission coil 41 provided inthe road surface and the power reception coil 51. For this reason, thewireless power reception system 1 can improve the power receptionefficiency in wireless power transfer.

Also, according to the wireless power reception system 1 embodied asillustrated in FIGS. 2 to 6 , the power reception coil 51 includes thestacked plurality of spiral coil layers 52 a and 52 b, and therefore thearea of the coil surface can be reduced compared to a power receptioncoil with a single-layer structure (a power reception coil having only asingle spiral coil layer) having similar power reception capability. Inother words, the number of windings in the power reception coil 51overall can be secured to obtain the power reception capability with theplurality of spiral coil layers 52 a and 52 b, while at the same time,the area of the coil surface of the power reception coil 51 can berestrained. For this reason, the degree of freedom with respect to theinstallation range of the power reception coil 51 is improved, making itpossible to house the power reception coil 51 over a wide range in thewheel 3. Also, since the area of the coil surface can be reduced,installation at a position close to the power transmission coil 41 iseasier, thereby further improving the power reception efficiency of thepower reception device 5.

In the wireless power reception system 1 embodied as illustrated inFIGS. 2 to 6 , the power reception coil 51 has a two-layer structureincluding the first spiral coil layer 52 a and the second spiral coillayer 52 b. According to such a configuration, the winding structure ofthe wire rod does not become complicated as readily as in the case ofproviding three or more spiral coil layers, making it easy tomanufacture the power reception coil 51.

In the wireless power reception system 1 embodied as illustrated inFIGS. 2 to 6 , the wire rod 53 forming the first spiral coil layer 52 aand the wire rod 53 forming the second spiral coil layer 52 b arecontinuous in the inner circumferential peripheral portion of the powerreception coil 51. According to such a configuration, a complicatedconfiguration of the power reception device 5 can be prevented comparedto the case where the first spiral coil layer 52 a and the second spiralcoil layer 52 b are independent from each other, and the overall powerreception device 5 can be given a simple configuration. Moreover, byproviding the connecting portion 54 on the inner circumferentialperipheral portion of the power reception coil 51, it is easier todispose the ends 53 a and 53 b of the wire rod 53 of the power receptioncoil 51 apart from each other. For this reason, since the distancebetween portions of the wire rod 53 can be secured appropriately, lossarising from a proximity effect can be reduced. As a result, the powerreception efficiency of the power reception device 5 can be improvedfurther.

In the wireless power reception system 1 embodied as illustrated inFIGS. 2 to 6 , the wire rod 53 forming the first spiral coil layer 52 aand the wire rod 53 forming the second spiral coil layer 52 b are formedby a single, continuous wire rod 53. According to such a configuration,the power transmission loss can be reduced compared to the case offorming the power reception coil 51 by joining a plurality of wire rods53. Furthermore, since joining a plurality of wire rods 53 isunnecessary, the manufacturing of the power reception coil 51 is alsoeasy.

In the wireless power reception system 1 embodied as illustrated inFIGS. 2 to 6 , the power reception coil 51 is provided with theplate-shaped case body 55 a (wire rod support portion) containing aninsulating material, and the wire rod 53 is disposed to follow thespiral grooves 55 g and 55 h formed in the case body 55 a. According tosuch a configuration, the wire rod 53 forming the power reception coil51 can be held in a stable state. Additionally, since the distancebetween portions of the wire rod 53 forming the power reception coil 51can be secured appropriately, loss arising from a proximity effect canbe reduced. As a result, the power reception efficiency of the powerreception device 5 can be improved further.

In the wireless power reception system 1 embodied as illustrated inFIGS. 2 to 6 , the spiral grooves 55 g and 55 h are formed on the frontand back surfaces, respectively, of the case body 55 a, such that thespiral groove 55 g formed on the front surface and the spiral groove 55h formed on the back surface communicate through the through-hole 55 kformed in the case body 55 a. According to such a configuration, bydisposing the wire rod 53 to follow the spiral groove 55 g on the frontsurface and the spiral groove 55 h on the back surface of the case body55 a, the stacked plurality of spiral coil layers 52 a and 52 b can beformed easily. Moreover, by passing the wire rod 53 through thethrough-hole 55 k, the first spiral coil layer 52 a on the front sideand the second spiral coil layer 52 b on the back side of the case body55 a can be made to be continuous easily.

The moving body 2 embodied as illustrated in FIGS. 2 to 6 includes: thewheel 3; the power reception device 5 including the power reception coil51 that receives power supplied wirelessly from the power transmissioncoil 41 of the power transmission device 4 installed in a road surface,at least a portion of the power reception coil 51 being housed in thewheel 3; and the onboard device 6 electrically connected to the powerreception device 5, wherein the power reception device 5 can transmitreceived power to the onboard device 6, and the power reception coil 51includes the stacked plurality of spiral coil layers 52 a and 52 b.According to such a configuration, by housing at least a portion of thepower reception coil 51 in the wheel 3 that directly contacts the roadsurface, it is possible to lower the possibility that an obstacle willcome into the space between the power transmission coil 41 provided inthe road surface and the power reception coil 51. For this reason, themoving body 2 can improve the power reception efficiency in wirelesspower transfer. Also, the power reception coil 51 includes the stackedplurality of spiral coil layers 52 a and 52 b, and therefore the area ofthe coil surface as viewed from the axial direction of the powerreception coil 51 can be reduced compared to a power reception coil witha single-layer structure having similar power reception capability. Forthis reason, the degree of freedom with respect to the installationrange of the power reception coil 51 is improved, making it possible tohouse the power reception coil 51 over a wide range in the wheel 3.Also, installation at a position close to the power transmission coil 41is easier, thereby further improving the power reception efficiency ofthe power reception device 5.

The wheel 3 embodied as illustrated in FIGS. 2 to 6 is a wheel 3 of themoving body 2 and includes: the power reception device 5 including thepower reception coil 51 that receives power supplied wirelessly from thepower transmission coil 41 of the power transmission device 4 installedin a road surface, wherein at least a portion of the power receptioncoil 51 is housed in the wheel 3, and the power reception coil 51includes the stacked plurality of spiral coil layers 52 a and 52 b.According to such a configuration, by housing at least a portion of thepower reception coil 51 in the wheel 3 that directly contacts the roadsurface, it is possible to lower the possibility that an obstacle willcome into the space between the power transmission coil 41 provided inthe road surface and the power reception coil 51. For this reason, thewheel 3 can improve the power reception efficiency in wireless powertransfer. Also, the power reception coil 51 includes the stackedplurality of spiral coil layers 52 a and 52 b, and therefore the area ofthe coil surface as viewed from the axial direction of the powerreception coil 51 can be reduced compared to a power reception coil witha single-layer structure having similar power reception capability. Forthis reason, the degree of freedom with respect to the installationrange of the power reception coil 51 is improved, making it possible tohouse the power reception coil 51 over a wide range in the wheel 3.Also, installation at a position close to the power transmission coil 41is easier, thereby further improving the power reception efficiency ofthe power reception device 5.

Also, the wireless power reception system 1 embodied as illustrated inFIGS. 7 and 8 includes: the power reception device 5 including the powerreception coil 51 that receives power supplied wirelessly from the powertransmission coil 41 of the power transmission device 4 installed in aroad surface, at least a portion of the power reception coil 51 beinghoused in the wheel 3 of the moving body 2; and the driving device 61which is installed in the wheel 3 and which drives the wheel 3 withpower received by the power reception device 5, wherein the powerreception device 5 is provided with the converter 56 a that converts ACpower generated in the power reception coil 51 into DC power and theinverter 56 b that can convert DC power from the converter 56 a into ACpower to transmit power to the driving device 61, at least a portion ofthe converter 56 a and at least a portion of the inverter 56 b arehoused in the wheel 3, the converter 56 a is positioned vertically abovethe power reception coil 51, and the inverter 56 b is positionedvertically above the converter 56 a. According to such a configuration,by housing at least a portion of the power reception coil 51 in thewheel 3 that directly contacts the road surface, it is possible to lowerthe possibility that an obstacle will come into the space between thepower transmission coil 41 provided in the road surface and the powerreception coil 51. For this reason, the wireless power reception system1 can improve the power reception efficiency in wireless power transfer.

Also, according to the wireless power reception system 1 embodied asillustrated in FIGS. 7 and 8 , by positioning the converter 56 avertically above the power reception coil 51 and positioning theinverter 56 b vertically above the converter 56 a, it is easier todispose the power reception coil 51 close to the power transmission coil41, and in addition, the power transfer from the power transmission coil41 to the power reception coil 51 is not inhibited as much by theinverter 56 b and the converter 56 a. Therefore, the power receptionefficiency can be raised. Also, since it is easier to dispose the powerreception coil 51 and the converter 56 a close to each other, powertransmission loss occurring when transmitting power from the powerreception coil 51 to the converter 56 a can be reduced. Moreover, it iseasy to shorten the power transmission pathway from the power receptioncoil 51 to the driving device 61 through the converter 56 a and theinverter 56 b. For this reason, the power transmission loss can bereduced, and it is easier to utilize the space inside the wheel 3effectively.

In the wireless power reception system 1 embodied as illustrated inFIGS. 7 and 8 , the converter 56 a and the inverter 56 b are provided onthe annular substrate 56 c disposed coaxially with the wheel 3.According to such a configuration, the converter 56 a and the inverter56 b can be installed efficiently around the axial part of the wheel 3,and the space inside the wheel 3 can be utilized effectively.

In the wireless power reception system 1 embodied as illustrated inFIGS. 7 and 8 , the driving device 61 is the direct drive motor 63disposed coaxially with the wheel 3. According to such a configuration,the torque of the direct drive motor 63 can be transferred to the wheel3 directly without going through an indirect mechanism (such as agearbox), and therefore motive power loss can be reduced to drive thewheel 3 efficiently.

In the wireless power reception system 1 embodied as illustrated inFIGS. 7 and 8 , the power reception device 5 includes the coil case 55that houses the power reception coil 51, and the coil case 55 isintegrated with or joined to the case 56 d that houses the converter 56a. According to such a configuration, it is easier to stabilize thepositional relationship between the power reception coil 51 and theconverter 56 a. Moreover, integrating the coil case 55 with the case 56d that houses the converter 56 a makes it easier to configure a compactpower reception device 5.

The moving body 2 embodied as illustrated in FIGS. 7 and 8 includes: thewheel 3; the power reception device 5 including the power reception coil51 that receives power supplied wirelessly from the power transmissioncoil 41 of the power transmission device 4 installed in a road surface,at least a portion of the power reception coil 51 being housed in thewheel 3; and the driving device 61 which is installed in the wheel 3 andwhich drives the wheel 3 with power received by the power receptiondevice 5, wherein the power reception device 5 is provided with theconverter 56 a that converts AC power generated in the power receptioncoil 51 into DC power and the inverter 56 b that can convert DC powerfrom the converter 56 a into AC power to transmit power to the drivingdevice 61, at least a portion of the converter 56 a and at least aportion of the inverter 56 b are housed in the wheel 3, the converter 56a is positioned vertically above the power reception coil 51, and theinverter 56 b is positioned vertically above the converter 56 a.According to such a configuration, by housing at least a portion of thepower reception coil 51 in the wheel 3 that directly contacts the roadsurface, it is possible to lower the possibility that an obstacle willcome into the space between the power transmission coil 41 provided inthe road surface and the power reception coil 51. For this reason, thewireless power reception system 1 can improve the power receptionefficiency in wireless power transfer. Also, by positioning theconverter 56 a vertically above the power reception coil 51 andpositioning the inverter 56 b vertically above the converter 56 a, it iseasier to dispose the power reception coil 51 close to the powertransmission coil 41, and in addition, the power transfer from the powertransmission coil 41 to the power reception coil 51 is not inhibited asmuch by the inverter 56 b and the converter 56 a. Therefore, the powerreception efficiency can be raised. Also, since it is easier to disposethe power reception coil 51 and the converter 56 a close to each other,power transmission loss occurring when transmitting power from the powerreception coil 51 to the converter 56 a can be reduced. Moreover, it iseasy to shorten the power transmission pathway from the power receptioncoil 51 to the driving device 61 through the converter 56 a and theinverter 56 b. For this reason, the power transmission loss can bereduced, and it is easier to utilize the space inside the wheel 3effectively.

The wheel 3 embodied as illustrated in FIGS. 7 and 8 is a wheel 3 of themoving body 2 and includes: the power reception device 5 including thepower reception coil 51 that receives power supplied wirelessly from thepower transmission coil 41 of the power transmission device 4 installedin a road surface; and the driving device 61 that drives the wheel 3with power received by the power reception device 5, wherein the powerreception device 5 is provided with the converter 56 a that converts ACpower generated in the power reception coil 51 into DC power and theinverter 56 b that can convert DC power from the converter 56 a into ACpower to transmit power to the driving device 61, the wheel 3 internallyhouses at least a portion of the converter 56 a and at least a portionof the inverter 56 b, the converter 56 a is positioned vertically abovethe power reception coil 51, and the inverter 56 b is positionedvertically above the converter 56 a. According to such a configuration,by housing at least a portion of the power reception coil 51 in thewheel 3 that directly contacts the road surface, it is possible to lowerthe possibility that an obstacle will come into the space between thepower transmission coil 41 provided in the road surface and the powerreception coil 51. For this reason, the wireless power reception system1 can improve the power reception efficiency in wireless power transfer.Also, by positioning the converter 56 a vertically above the powerreception coil 51 and positioning the inverter 56 b vertically above theconverter 56 a, it is easier to dispose the power reception coil 51close to the power transmission coil 41, and in addition, the powertransfer from the power transmission coil 41 to the power reception coil51 is not inhibited as much by the inverter 56 b and the converter 56 a.Therefore, the power reception efficiency can be raised. Also, since itis easier to dispose the power reception coil 51 and the converter 56 aclose to each other, power transmission loss occurring when transmittingpower from the power reception coil 51 to the converter 56 a can bereduced. Moreover, it is easy to shorten the power transmission pathwayfrom the power reception coil 51 to the driving device 61 through theconverter 56 a and the inverter 56 b. For this reason, the powertransmission loss can be reduced, and it is easier to utilize the spaceinside the wheel 3 effectively.

The present disclosure has been described on the basis of the drawingsand embodiments, but it should be noted that a person skilled in the artcould make various modifications and revisions on the basis of thepresent disclosure. Consequently, it should be appreciated that any suchmodifications or revisions are included in the scope of the presentdisclosure. For example, the components, functions, and the likeincluded in each embodiment or practical example may be rearranged inlogically non-contradictory ways. Moreover, the components, functions,and the like included in each embodiment can be used in combination withanother embodiment or practical example, and a plurality of components,functions, and the like may be combined into one, divided, or partiallyomitted.

For example, in the embodiments described above, some or all of thefunctions or processes described as functions or processes of thecontrol device 7 may also be achieved as functions or processes of thepower reception device 5 or the onboard device 6. For example, a programstating processing content for achieving each function of the controldevice 7 according to an embodiment may be stored in a memory or thelike provided in the power reception device 5 or the onboard device 6,and the program may be read out and executed by a processor or the likeof the power reception device 5 or the onboard device 6.

As another example, in the embodiments described above, the coil surfaceof the power reception device 5 is described as being disposedapproximately parallel to the contact patch of the wheel 3, but is notlimited thereto. The coil surface of the power reception coil 51 mayalso be disposed at any angle from 0 degrees to 90 degrees with respectto the contact patch of the wheel 3. The angle between the coil surfaceof the power reception coil 51 and the contact patch of the wheel 3 maybe freely determined according to the purpose of the power receptiondevice 5, the amount of power to be received, and the like.

As another example, in the embodiments described above, the tire 31 isdescribed as being filled with air, but is not limited thereto. Forexample, the tire 31 may be filled with a gas such as nitrogen. Asanother example, instead of or in addition to air, the tire 31 may befilled with any fluid, such as a liquid, a gelatinous material, orparticulate matter.

REFERENCE SIGNS LIST

-   -   1 wireless power reception system    -   2 moving body    -   21 hub    -   22 shaft    -   3 wheel    -   31 tire    -   311 bead portion    -   312 sidewall portion    -   313 tread portion    -   32 wheel    -   321 rim portion    -   322 disc portion    -   4 power transmission device    -   41 power transmission coil    -   5 power reception device    -   51 power reception coil    -   52 a first spiral coil layer    -   52 b second spiral coil layer    -   56 a converter    -   56 b inverter    -   6 onboard device    -   61 driving device    -   62 power storage device    -   7 control device    -   71 control unit    -   72 storage unit    -   73 communication unit    -   74 output unit    -   75 input unit

1. A wireless power reception system comprising: a power receptiondevice including a power reception coil configured to receive powersupplied wirelessly from a power transmission coil of a powertransmission device installed in a road surface, at least a portion ofthe power reception coil being housed in a wheel of a moving body; andan onboard device installed in the moving body, the onboard device beingelectrically connected to the power reception device, wherein the powerreception device is capable of transmitting the received power to theonboard device, and the power reception coil has a convex shape pointingdownward in a side view as seen from an axial direction of the wheel. 2.The wireless power reception system according to claim 1, wherein thepower reception coil is curved into an arc shape in the side view. 3.The wireless power reception system according to claim 2, wherein acenter of curvature of the power reception coil in the side view islocated on a central axis of the wheel.
 4. The wireless power receptionsystem according to claim 1, wherein the power reception coil includes astacked plurality of spiral coil layers.
 5. A moving body comprising: awheel; a power reception device including a power reception coilconfigured to receive power supplied wirelessly from a powertransmission coil of a power transmission device installed in a roadsurface, at least a portion of the power reception coil being housed inthe wheel; and an onboard device electrically connected to the powerreception device, wherein the power reception device is capable oftransmitting the received power to the onboard device, and the powerreception coil has a convex shape pointing downward in a side view asseen from an axial direction of the wheel.
 6. A wheel of a moving bodycomprising: a power reception device including a power reception coilconfigured to receive power supplied wirelessly from a powertransmission coil of a power transmission device installed in a roadsurface, wherein at least a portion of the power reception coil ishoused internally, and the power reception coil has a convex shapepointing downward in a side view as seen from an axial direction of thewheel.
 7. The wireless power reception system according to claim 2,wherein the power reception coil includes a stacked plurality of spiralcoil layers.
 8. The wireless power reception system according to claim3, wherein the power reception coil includes a stacked plurality ofspiral coil layers.